The Journal of Neuroscience, September 15, 2000, 20(18):7011-7016
Stimulus-Based State Control in the Thalamocortical System
Lee M.
Miller and
Christoph E.
Schreiner
W. M. Keck Center for Integrative Neuroscience, and University
of California San Francisco/Berkeley Bioengineering Group, University
of California Medical Center, San Francisco, California 94143
Neural systems operate in various dynamic states that determine how
they process information (Livingstone and Hubel, 1981; Funke and Eysel,
1992; Morrow and Casey, 1992; Abeles et al., 1995; Guido et al., 1995;
Mukherjee and Kaplan, 1995; Kenmochi and Eggermont, 1997;
Wörgötter et al., 1998; Kisley and Gerstein, 1999). To
investigate the function of a brain area, it is therefore crucial to
determine the state of that system. One grave difficulty is that even
under well controlled conditions, the thalamocortical network may
undergo random dynamic state fluctuations which alter the most
basic spatial and temporal response properties of the neurons. These
uncontrolled state changes hinder the evaluation of state-specific
properties of neural processing and, consequently, the interpretation
of thalamocortical function.
Simultaneous extracellular recordings were made in the auditory
thalamus and cortex of the ketamine-anesthetized cat under several
stimulus conditions. By considering the cellular and network mechanisms
that govern state changes, we develop a complex stimulus that controls
the dynamic state of the thalamocortical network. Traditional auditory
stimuli have ambivalent effects on thalamocortical state, sometimes
eliciting an oscillatory state prevalent in sleeping animals and other
times suppressing it. By contrast, our complex stimulus clamps the
network in a dynamic state resembling that observed in the alert
animal. It thus allows evaluation of neural information processing not
confounded by uncontrolled variations. Stimulus-based state control
illustrates a general and direct mechanism whereby the functional modes
of the brain are influenced by structural features of the external world.
Key words:
dynamic state; thalamocortical; spindles; oscillations; ketamine; alerting stimuli; burst mode; tonic mode
Copyright © 2000 Society for Neuroscience 0270-6474/00/20187011-06$05.00/0
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